ACACIA CY6033

Inclusion Criteria:
*  Between 18-85 years of age
*  Body mass index \< 40 kg/m2
*  Diagnosed with nHCM and has a screening echocardiogram with the following:
*  End-diastolic left ventricular (LV) wall thickness:
*  ≥ 15 mm in one or more myocardial segments OR
*  ≥ 13 mm in one or more wall segments and a known disease-causing gene mutation or positive family history of HCM AND
*  Resting LVOT-G \< 30 mmHg AND Valsalva LVOT-G \< 50 mmHg AND
*  LVEF ≥ 60%
*  Participants with a history of intracavitary obstruction are eligible.
*  NYHA class II or III
*  Respiratory exchange ratio of ≥ 1.00 at screening by cardiopulmonary exercise testing (CPET) and predicted peak oxygen uptake (pVO2) ≤ 90% for age and sex
*  KCCQ-CSS score of ≥ 30 and ≤ 85
*  NT-proBNP of:
*  NT-pro BNP ≥ 300 pg/mL or NT-proBNP ≥ 900 pg/mL if in atrial fibrillation or atrial flutter OR
*  For Black participants, an NT-pro BNP ≥ 225 pg/mL or NT-proBNP ≥ 675 pg/mL if in atrial fibrillation or atrial flutter

Exclusion Criteria:
*  Significant valvular heart disease (per Investigator judgment)
*  Moderate or severe valvular aortic stenosis or fixed subaortic obstruction
*  Moderate or severe mitral regurgitation
*  Known or suspected infiltrative, genetic or storage disorder causing cardiac hypertrophy that mimics nHCM (eg, Noonan syndrome, Fabry disease, amyloidosis)
*  Known current unrevascularized coronary artery stenosis of ≥ 70% or documented history of myocardial infarction.
*  History of LV systolic dysfunction (LVEF \< 45%) or stress cardiomyopathy
*  Inability to exercise on a treadmill or bicycle (eg, orthopedic limitations)
*  Documented room air oxygen saturation reading \< 90% at screening or history of significant chronic obstructive pulmonary disease or severe/significant pulmonary hypertension
*  History of syncope, symptomatic ventricular arrhythmia, or sustained ventricular tachyarrhythmia with exercise within 3 months prior to screening
*  History of resistant hypertension (persistently elevated blood pressure despite maximal doses of 3 or more classes of medications for hypertension control)
*  Screening diastolic blood pressure ≥ 100 mmHg
*  Received prior treatment with aficamten
*  Received treatment with mavacamten within 3 months prior to screening (must be discussed with the medical monitor prior to screening)
*  Undergone septal reduction therapy \< 6 months prior to screening
*  Is being considered for or is likely to be considered for heart transplant listing or left ventricular assist device placement during the study period
*  Paroxysmal or permanent atrial fibrillation is excluded only if:
*  rhythm restoring treatment (e.g., direct-current cardioversion, atrial fibrillation ablation procedure, or antiarrhythmic therapy) has been required ≤ 3 months prior to screening
*  rate control and anticoagulation have not been achieved for at least 3 months prior to screening.